Conventionally, there has been known an image forming device having a function of automatically switching a cassette from which sheets are fed (this function being referred to as an APS or automatic cassette change hereinafter). In such an image forming device, where sheets having the same size, the same direction, and the same type (quality, thickness and the like of sheets) are stored in a plurality of cassettes, when sheets stored in one cassette are used up, sheet feeding is automatically switched such that sheets are fed from another cassette and the formation of images can be continued.
In a conventional image forming device having the APS, when sheets of the same kind are stored in a plurality of cassettes, sheet feeding is performed by assigning priority to an upper cassette, that is, the cassette arranged closest to an image forming unit of the image forming device. This is because a time required for a sheet to arrive at the image forming unit is shorter in case of the sheet being fed the upper cassette compared to a lower cassette. Further, on a display screen which allows a user to select the cassette from which sheets are fed, the layout of the image forming device is made such that the user is likely to select the upper cassette, and hence the user tends to select the upper cassette.
Accordingly, sheets stored in the upper cassette are likely to be used up earlier than sheets stored in the lower cassettes. Thus, in an automatic cassette change which is performed when the stored sheets are used up, the sheet feeding cassette tends to be switched from an upper cassette to a lower cassette in many cases.